The concept of ethane pyrolysis to produce ethyne is known. In British Patent No. 1,335,892 a process for the preparation of ethyne by pyrolysis of ethane is disclosed comprising heating for a period of time that is less than 0.1 sec. for instance, 0.07 sec, a pre-heated mixture of ethane and steam in a weight ratio of 1:2-3 at a temperature between 1000 and 1100.degree. C, in a tubular reactor having an internal diameter of at most 5 cm. According to this document, the internal diameter must not exceed 5 cm, because the desired temperature will otherwise not be attained whereas the claimed weight ratio of ethane to steam is essential to limit coke formation. During the pre-heating of the mixture, steam should be present because of this coke formation. The example illustrates the preparation of ethyne in a yield of 13.5% wt (on the total effluent after drying).
In U.S. Pat. No. 3,116,344 a process for the preparation of ethyne by pyrolysis of ethane is disclosed of excellent ethyne selectivity through the pyrolysis of a pre-heated mixture in the absence of oxygen or oxygenated dissociation products (e.g., steam) using a vortex tube reactor. However, the mass balance does not mention the amount of coke and it will be realized (in view of the teaching of British patent No. 1,335,892) that coke formation (being a sink of feedstock and a pollutant of the reactor) will be substantial. Example II (best) illustrates the preparation of ethyne in a yield of 50.1% wt (on the total effluent), however, not corrected for the formation of coke.
Thus, although the conditions favoring the formation of ethyne by pyrolysis of ethane are known, heating the same for a period of time less than 0.5 sec at a temperature of say 950 to 1500.degree. C., it remains desirable to produce ethyne in still higher selectivity and yield, i.e., avoiding the formation of coke.